1. Field of the Invention
The present invention relates to a thermal printer in which printing is performed while paper is sandwiched between a thermal head and a platen roller, and more particularly to a technique usefully utilized in a printer in which bar-code printing is performed, for example.
2. Description of the Related Art
Thermal printers, in which printing is performed by pressing thermal recording paper between a thermal head having a heating element and a platen roller, are often applied to, for example, a printer for performing receipt-printing in a cash register and a portable label printer for performing printing of POS labels for foods and labels for distribution management.
A conventional thermal printer is structured such that a thermal head is fixed to a head support body that also serves as a heat radiating plate; the head support body is rotatably supported with a shaft by means of a frame or the like of the printer; and further, the head support body is biased by a spring or the like to be pressed against a platen roller side (for example, refer to JP 04-140175 A).
In the conventional thermal printer, in the case where failure is caused in printing dots of a thermal head due to the influence of, for example, over electrification and damage on paper, there is no way but to disassemble the whole printer and exchange the thermal head. Such work has been extremely troublesome.
In particular, in the conventional thermal printer, a metal fitting with an E-shape which is so called E-ring is fastened to a shaft with which a head support body is axially supported by a frame such that the shaft is not slid horizontally; alternatively, a support shaft, which is provided to be projected from right and left side surfaces of the head support body, is press-fitted in a bearing provided in the frame to be fixed. That is, the conventional thermal printer has a structure in which a thermal head cannot be disassembled easily. It has been impossible that only the thermal head portion is removed while the thermal printer is being incorporated in a main body apparatus.
Generally, a thermal printer that performs printing of characters and the like does not particularly require an exchange of a thermal head when at least printing failure with one dot occurs. However, in recent years, a label printer that performs label printing for distribution management may involve bar-code printing. There is a fear that a problem develops even with a little dot chip when the bar-code printing will be performed with fine lines in the future. Therefore, it is considered that how frequently the exchange of the thermal head due to wrong dots or the like is increased more than before.